GB2634250A

GB2634250A - An operating method for a wearable air purifier

Info

Publication number: GB2634250A
Application number: GB2315143.4A
Authority: GB
Inventors: Knight Reid Peter; Stephen Darling Philip
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2023-10-03
Filing date: 2023-10-03
Publication date: 2025-04-09
Also published as: WO2025074237A1; GB202315143D0

Abstract

The head wearable air purifier comprises a speaker assembly, a microphone assembly, and a fan assembly operable to generate filtered airflow towards the face of a wearer. The physical state of the head wearable air purifier amongst a plurality of known physical states is determined, preferably by detecting the fan speed. Each such state producing different acoustic characteristics of the head wearable air purifier. An audio profile associated with the determined physical state of the head wearable air purifier is obtained from a set of stored profiles 224, and an audio signal from the microphone assembly 210 is modified 223 based on the obtained audio profile. The modified audio signal is then output 230. A head wearable air purifier for implementing the method is also described.

Description

AN OPERATING METHOD FOR A WEARABLE AIR PURIFIER

BACKGROUND

Air pollution is an increasing problem and a variety of air pollutants have known or suspected harmful effects on human health. The adverse effects that can be caused by air pollution depend upon the pollutant type and concentration, and the length exposure to the polluted air. For example, high air pollution levels can cause immediate health problems such as aggravated cardiovascular and respiratory illness, whereas long-term exposure to polluted air can have permanent health effects such as loss of lung capacity and decreased lung function, and the development of diseases such as asthma, bronchitis, emphysema, and possibly cancer.

In locations with particularly high levels of air pollution, many individuals have recognised the benefits of minimising their exposure to these pollutants and have therefore taken to wearing face masks with the aim of filtering out at least a portion of the pollutants present in the air before it reaches the mouth and nose. These face masks range from basic dust masks that merely filter out relatively large dust particles, to more complex air-purifying respirators that require that the air pass through a filter element or cartridge.

There have been various attempts to develop air purifiers that can be worn by the user but that do not require the user's mouth and nose to be covered. For example, there are various designs for wearable air purifiers that are worn around the neck of the user and that create a jet of air that is directed upwards towards the user's mouth and nose. Other headset arrangements have been developed in which both a fan and a filter are incorporated into at least one of the earcups of a set of headphones.

SUMMARY

According to a first aspect of the present invention, there is provided a method of operating a head wearable air purifier comprising a speaker assembly (for example, wherein the speaker assembly is arranged to be worn over an ear of a user, sometimes referred to herein as a wearer), a microphone assembly and a fan assembly operable to generate filtered airflow towards the face of a wearer, for example for inhalation by the wearer, wherein the method comprises determining a physical state of the head wearable air purifier amongst a plurality of known physical states, each known physical state producing different acoustic characteristics of the head wearable air purifier; receiving an audio signal from the microphone assembly; obtaining an audio profile associated with the determined physical state of the head wearable air purifier; modifying the audio signal based on the audio profile; and outputting the modified audio signal. The audio signal is a digital signal (e.g., an electrical or binary signal) representative of sound detected by the microphone assembly, wherein the sound may contain speech, for example speech of a wearer of the head wearable air purifier or speech of another person who is talking to the wearer, in addition to noise (e.g., noise generated by the head wearable air purifier or external sources). Each of the known physical states may produce different acoustic characteristics of the head wearable air purifier that are discernibly different to a person (e.g., to wearer hearing sound and noise from the environment surrounding the head wearable air purifier, or to another person talking to the wearer over a telephony system and so hearing the wearer's voice as well as noise generated by the head wearable air purifier). The acoustic characteristics may comprise noise present in the audio signal, such as noise generated by the head wearable air purifier (e.g., generated by the fan assembly) which may be audible to a person hearing an outputted audio signal, an impact (e.g., a change of frequency, pitch, amplitude, loudness, duration, tone, timbre, texture, additional unwanted noise etc.) on sounds generated external to the head wearable air purifier (for example, sounds generated by a wearer of the head wearable air purifier or by another person; such as speech) resulting from the physical state of the head wearable air purifier. In particular, the acoustic characteristics due to the physical state may affect sound picked up by the microphone assembly and represented by the received audio signal. In this way, modification of an audio signal may be carried out based on a detected physical state of the head wearable air purifier, rather than performing active noise cancellation as in known arrangements. This provides a computationally efficient manner in which to account for different acoustic characteristics of the head wearable air purifier. Furthermore, the method may more effectively account for noise generated by the head wearable air purifier itself, which may be present in the audio signal and masking or distorting a desired part of the audio signal (such as speech).

Optionally, the determining the physical state of the head wearable air purifier may comprise determining a rotation speed of the fan assembly. For example, this may comprise determining the rotational speed of a rotating component, such as a fan (e.g., an impeller or compressor) of the fan assembly. In particular, rotation of the fan assembly may affect acoustic characteristics of the head wearable air purifier by generating noise which can have a detrimental effect on sound detected by the microphone assembly (e.g., noise from the fan assembly may impact sound from an environment surrounding the head wearable air purifier, particularly where that sound is speech from a person speaking to a user of the head wearable air purifier), and the acoustic characteristics (e.g., volume, frequency) of the noise may be dependent on the rotation speed.

Optionally, determining the rotation speed of the fan assembly may comprise determining a predetermined rotation speed of the fan assembly based on a known rotation speed setting of the fan assembly. For example, this may comprise determining a rotation speed of a fan (e.g., an impeller or compressor) of the fan assembly. For example, a rotation speed setting may be determined from software instructions for a controller (e.g., a motor controller) of the fan assembly. As the rotation speed is predetermined and based on a known rotation speed setting, the audio profile may be obtained (e.g., retrieved from a look-up table) easily, and the audio profile may be particularly effective at modifying the audio signal for the particular acoustic characteristics.

Optionally, determining the rotation speed of the fan assembly may comprise determining whether the fan assembly is not rotating, rotating at a low speed, rotating at a medium speed, or rotating at a high speed. For example, this may comprise determining whether a fan (e.g., an impeller or compressor) of the fan assembly is not rotating, rotating at a low speed, rotating at a medium speed, or rotating at a high speed. When the fan assembly is not rotating, this may be indicative of an 'off' state of the fan assembly, for example.

In certain embodiments, the audio profile may comprise a filter to be applied to the audio signal to remove unwanted noise introduced to the audio signal by rotation of the fan assembly (for example, a rotating component, such as a fan (e.g., an impeller or compressor) of the fan assembly). By obtaining a filter in response to determining a rotation speed of the fan assembly in this way, the method may be able to effectively reduce the noise in the audio signal resulting from the rotation of the fan assembly in a manner which is more computationally efficient than by using known active noise control methods. For example, obtaining and applying a filter may use less computer resources than an active noise control method, which may help to reduce power consumption of the head wearable air purifier. In addition, in certain embodiments the fan assembly may be determined to have a predetermined rotation speed, and so an appropriate filter can be stored (e.g., in a memory or storage) which corresponds with the predetermined rotation speed.

Optionally, the filter may be a notch filter configured to filter out any one or more of a plurality of fundamental or harmonic tones in the audio signal resulting from rotation of the fan assembly. For example, a notch filter may be configured to filter out the noise associated with a fundamental or a harmonic tone. A plurality of such notch filters may be used to filter out noise above a predetermined amplitude level, for example the predetermined amplitude level may be defined by a broadband noise floor of the filter assembly, such that all harmonics greater in amplitude than this noise floor are filtered by a corresponding notch filter. It will be appreciated that the noise floor, and the audibility of noise generated by the fan assembly, will vary dependent on a motor of the fan assembly, a motor speed, and a method of assembly (e.g, the presence of any noise damping material, noise leakage from the fan assembly).

Optionally, a bandwidth of the notch filter may be determined according to a frequency of the fundamental or harmonic tone and the precision to which a rotation speed of the fan assembly is determined. In particular, the precision to which a rotation speed of the fan assembly is determined may be dependent upon the precision to which a rotation speed of the fan assembly is controlled, for example where the rotation speed is determined from software instructions for a controller (e.g., a motor controller) of the fan assembly. For example, if the rotation speed of the fan can be determined (e.g., controlled) to +1-5% of a desired value, and the frequency of noise generated is 100 Hz, then the bandwidth of the notch filter may be 10 Hz, and if the frequency of the noise generated is 500 Hz then the bandwidth of the notch filter may be 50 Hz. By being provided in this way, the notch filter may be configured to remove only the noise generated by rotation of the fan assembly, and will have a limited effect on the desired features of the audio signal (thereby, for example, retaining naturalness of sound represented by an audio signal, such as speech).

Optionally, modifying the audio signal may further comprise applying a noise reduction algorithm. For example, this may be a wind noise reduction algorithm or the like.

Optionally, determining the physical state of the head wearable air purifier may comprise determining a presence of and/or a position of a nozzle assembly, wherein the nozzle assembly is attachable to the fan assembly to receive airflow generated by the fan assembly and discharge the airflow towards a face of a wearer. For example, a nozzle assembly may produce different acoustic characteristics of the head wearable air purifier which affect the voice of a wearer, which may affect how the voice of a wearer is heard by another person (e.g., via a telephony system). By being provided in this way, the present invention may allow the acoustic impact of the nozzle assembly to be mitigated by applying an appropriate audio profile to the audio signal Optionally, the audio profile may comprise an equalisation profile to be applied to the audio signal to compensate for distortions in the sound represented by the audio signal by the nozzle assembly. In certain embodiments, the equalisation profile may be configured to adjust the gain and/or the frequency response.

Optionally, the audio signal may be received from at least one of an external microphone of the head wearable air purifier configured to target detection of a wearer's voice or an external microphone of the head wearable air purifier configured to target detection of sound from an environment surrounding the head wearable air purifier (which may, for example, include speech of a person speaking to a user of the head wearable air purifier). An internal microphone may be understood as being internal to the speaker assembly, for example a microphone which is acoustically connected to an internal volume of the head wearable air purifier (e.g., a surface or volume of the head wearable air purifier which is acoustically connected to the speaker assembly and/or the fan assembly). For example, an internal microphone may be configured to detect noise from the fan assembly (e.g., noise generated by a motor or an impeller of the fan assembly). An external microphone may be understood as being external to the speaker assembly, and is thereby a microphone which is acoustically connected to an external, environmental, or ambient volume. For example, the external microphone may be configured to pick up ambient sound and noise of the environment surrounding the head wearable air purifier. Another example of an external microphone may be a microphone which is configured to target detection of a wearer's voice, such as a directional microphone.

Optionally, outputting the modified audio signal may comprise outputting the modified audio signal to the speaker assembly (for example, operating the speaker assembly according to the modified audio signal). For example, this may be particularly advantageous wherein the audio signal is received from an external microphone configured to detect ambient sound and noise, such that the modified audio signal may provide to the user (e.g., through the speaker assembly) an enhanced audio signal based on sound from the environment surrounding the head wearable air purifier, without the disruptive effect of the acoustic characteristics of the head wearable air purifier (e.g., noise generated by the fan assembly).

Optionally, modifying the audio signal may further comprise applying a noise reduction algorithm, and wherein the noise reduction algorithm is applied in the time domain.

Applying a noise reductive algorithm in the time domain may reduce latency associated with application of the noise reduction algorithm. This may be particularly advantageous for a user to hear an audio signal based on sound from the environment surround the head wearable air purifier as soon as possible, for example in order to ensure naturalness of the sound heard by a user.

Optionally, modifying the audio signal may further comprise applying an equalisation profile and/or a compression profile.

Optionally, outputting the modified audio signal may comprise outputting the modified audio signal to a telephony system of the head wearable air purifier. For example, this may be particularly suitable where the audio signal is received from an external microphone, which may detect a wearer's voice. The modified audio signal may therefore provide an enhanced audio signal to a receiver of a telephone call from a wearer, in which the voice of the wearer has improved clarity and naturalness without the disruptive acoustic characteristics of the head wearable air purifier (e.g., noise generated by the fan assembly and/or an effect of a nozzle assembly on the voice of a wearer as detected by an internal microphone).

Optionally, modifying the audio signal may further comprise applying a noise reduction algorithm, and wherein the noise reduction algorithm is applied in the frequency domain. This may be particularly suitable when the audio signal is output to a telephony system of the head wearable air purifier, as this may increase the efficacy of the noise reduction algorithm, and reducing latency is a lower priority due to the reduced latency inherent in the telephony system.

Optionally, modifying the audio signal may further comprise applying a beamforming algorithm. For example, the beamforming algorithm may be configured to target or isolate the voice of a wearer and dimmish other sounds or noise in the audio signal According to a second aspect of the present invention, there is provided a head wearable air purifier comprising: a speaker assembly arranged to be worn by a wearer; a fan assembly operable to generate filtered airflow and discharge the filtered airflow towards the face of a wearer; a microphone assembly for obtaining an audio signal; and a controller configured to perform a method according to any one of the preceding claims. In this way, the present invention provides a head wearable air purifier in which acoustic changes resulting from a physical state of the head wearable air purifier may be compensated for in a more efficient and effective manner (e.g., more computationally efficient, thereby saving power) than known arrangements. In some examples, the fan assembly may be removably attachable to the speaker assembly.

Optionally, the head wearable air purifier may further comprise a nozzle assembly, the nozzle assembly comprising an air inlet for receiving a purified airflow from the fan assembly and an air outlet for directing the purified airflow towards a wearer's mouth, wherein the nozzle assembly is removably attachable to the head wearable air purifier. By providing a nozzle assembly, purified airflow may be more effectively delivered to a wearer's nose and mouth. However, the physical state of the nozzle assembly may have an effect on the acoustic characteristics of the head wearable air purifier (in particular, may have an effect on the sound of a wearer's voice). This effect may be compensated by the head wearable air purifier by performing a method according to the first aspect of the present invention, that is, by obtaining an audio profile associated with the physical state and modifying the audio signal (e.g., a signal relating to the voice of a wearer) based on the audio profile.

Optionally, the microphone assembly may comprise at least one of: a microphone which is internal to the speaker assembly; and/or a microphone which is external to the speaker assembly. For example, the microphone assembly may comprise a first external microphone which may be arranged to detect ambient sound and noise, a second external microphone for detecting the voice of a wearer, and an internal microphone for detecting noise from the fan assembly.

The term "air purifier" as used herein refers to a device or system capable of removing contaminants from air and emitting a supply of purified or filtered air. The term "head wearable" is used herein to define an item as being capable of or suitable for being worn on the head of a user.

The invention includes the combination of the aspects and optional features described except where such a combination is impermissible or expressly avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure la is a front perspective view of an embodiment of a head wearable air purifier as described herein; Figure lb is a front view of the head wearable air purifier of Figure la; Figure lc is a front perspective view of the head wearable air purifier of Figure la with the nozzle assembly stowed over the headband; Figure 2 is a cross-sectional view of an ear cup of the head wearable air purifier of Fig. I a; Figure 3 is a flow chart showing a method of operating a head wearable air purifier according to an embodiment of the present invention; Figure 4 is a schematic diagram of a method according to an embodiment of the present invention; Figure 5 is a schematic diagram of a method according to a further embodiment of the present invention; Figure 6 is a graph of amplitude against frequency showing a change in acoustic characteristics of a head wearable air purifier due to a nozzle assembly; and Figure 7 is a graph of amplitude against frequency showing a notch filter which may be used in embodiments of the present invention.

DETAILED DESCRIPTION

The head wearable air purifier comprises a headphone system comprising a pair of ear cups 30 mounted on a headband. A first ear cup is mounted on a first end of the headband and a second ear cup is mounted on an opposite, second end of the headband. One or both of the first ear cup and the second ear cup then comprises a fan assembly and a speaker assembly, wherein the fan assembly comprises a filter assembly, an impeller for creating an airflow through the filter assembly, a motor arranged to drive the impeller and an air outlet downstream from the filter assembly for emitting the filtered airflow from the speaker assembly. The impeller is a mixed flow impeller that has a generally conical or frusto-conical shape, and both the impeller and the motor are disposed within an impeller casing that is generally frusto-conical in shape. The fan assembly may be removably attachable to the ear cup, such as by being removably connectable to the speaker assembly. The head wearable air purifier then further comprises a nozzle assembly arranged to receive the filtered airflow from one or both of the first speaker assembly and the second speaker assembly, the nozzle comprising an air outlet arranged to emit the received filtered airflow from the head wearable air purifier.

The term "headphones" as used herein refers to a pair of small loudspeakers, or speakers, joined by a headband that is designed to be worn on or around the head of a user. Typically, the speakers are provided by electroacoustic transducers that convert an electrical signal to a corresponding sound. Circumaural headphones, often referred to as full-size or over-ear headphones, have earpads whose shape is that of a closed loop (e.g. circular, elliptical etc.) so that they encompass the entire ear. Because these headphones completely surround the ear, circumaural headphones can be designed to fully seal against the head to attenuate external noise. Supra-aural headphones, often referred to as on-ear headphones, have earpads that press against the ears, rather than around them. This type of headphone generally tends to be smaller and lighter than circumaural headphones, resulting in less attenuation of outside noise.

For example, the physical features of the head wearable air purifier may be substantially as described in W02020021232A1.

Figures la, lb and lc are external views of an embodiment of a head wearable air purifier 1000. The head wearable air purifier 1000 comprises a pair of generally cylindrical ear cups 1100a, 1100b connected by an arcuate headband 1200, and a nozzle assembly 1300 that extends between and is connected at opposite ends to both ear cups 1100a, 1100b.

In the illustrated embodiment, each end of the headband 1200 is provided with an arcuate support arm 1201a, 1201b that is perpendicular to the headband 1200 (i.e. such that the plane that is parallel to the length of the arcuate headband 1200 is perpendicular to the plane that is parallel to the length of the arcuate support arm 1210). A first end of each support arm 1201a, 120 lb is attached to a rear surface of the headband 1200 such that the support arm 1201a, 120 lb extends rearward and downward from the headband 1200. An opposite, second end of each support arm 1201a, 1201b is then provided with a socket or gudgeon 1202a, 1202b that faces forward. The socket/gudgeon 1202a, 1202b provided on each of the support arms 1201 is configured to receive and retain a projection/pintle that projects from the outer surface of the corresponding ear cup 1100. The engagement of the projections within sockets provided on the support arms 1201 therefore forms a gimbal or hinge that pivotally supports the ear cups 1100 when attached to the ends of headband 1200.

As shown in Fig. 2, each of the pair of ear cups 1100 comprises a speaker assembly, the speaker assembly comprising speaker housing or enclosure 1102 having an air inlet 1103 and an air outlet or discharge port 1104, a speaker or driver unit 1105 within the housing 1102, and an earpad 1106 arranged to enclose the speaker 1105 and to encompass or press against an ear of a user. In addition, each of the pair of ear cups 1100 further comprises a fan assembly, which may be removably attachable to the ear cups 1100. The fan assembly comprises a filter assembly 1107 within speaker housing 1102 and an impeller casing 1108 within the speaker housing 1102. Disposed within the impeller casing 1108 is an impeller 1109 for creating an airflow through the filter assembly 1107 and a motor 1110 arranged to drive the impeller 1109. The air outlet or discharge port 1104 is downstream (i.e. relative to the airflow generated by the impeller 1109) from the filter assembly 1107 and is arranged to emit the filtered/purified airflow from the ear cup 1100. In the illustrated embodiment, the air outlet or discharge port 1104 of each ear cup 1100 is provided in a side of the ear cup 1100, with the air outlet or discharge port 1104 of both ear cups 1100a, 1100b being generally parallel with one another when attached to the ends of headband 1200.

In addition, an internal microphone can be provided for detecting noise from the fan assembly, for example on the driver support plate 1111d of the speaker chassis. The internal microphone is arranged to provide data to a control circuit 1114, with the control circuit 1114 then being configured to implement a control method as described below when controlling the speaker/driver unit 1105. The internal microphone is disposed within a corresponding aperture provided in the driver support plate 1111d. Providing the ear cup 1100 with an internal microphone in this way is particularly useful, as it provides that acoustic characteristics such as noise generated by the motor 1110 and/or the impeller 1109 can be detected by the internal microphone 1113 and removed from an audio signal. In particular, the microphone helps with this noise reduction by monitoring the actual motor 1110/impeller 1109 in real time.

A control circuit 1114 is disposed on or mounted to the peripheral portion of the speaker chassis 1111. The control circuit 1114 therefore at least partially encircles the speaker/driver unit 1105 (i.e. is disposed outside/around a periphery of the speaker/driver unit 1105) when the speaker/driver unit 1105 is mounted on to the driver support plate 1111d. In the illustrated embodiment, the control circuit 1114 comprises two arcuate circuit boards 1114a, 1114b; however, in alternative arrangements the control circuit 1114 could equally comprise more than two arcuate circuit boards or a single arcuate or annular circuit board.

The control circuit 1114 controls both the motor 1110 and the speaker/driver unit 1105 based on control inputs received from a user. The control circuit 1114 also provides one or more wireless communication modules that allows the purifier 1000 to connect to one or more wireless networks using Wi-H, Bluetooth or some other form of wireless personal area network (WPAN). A user of the purifier 1000 can then wirelessly connect to and communicate with the purifier 1000 using a personal computer device so that they can send and receive data to and from the purifier 1000, provide user inputs etc. The control circuit 1114 may also have a wired connection (not shown) to a touch screen and/or one or more physical user control devices (not shown) that are provided on the purifier 1000 and/or that are accessible to the user.

The ear cup 1100 is also provided with a hollow, rigid outlet duct 1115 that extends from the speaker housing 1102 and that is arranged to connect the air outlet 1104 of the ear cup 1100 to an air inlet of the nozzle assembly 1300. The rigid outlet duct 1115 is further arranged so that it can revolve relative to the speaker housing 1102, around at least a portion of the periphery of the speaker housing 1102, so that the angle between the nozzle assembly 1300 and the headband 1200 can be changed and so that the nozzle assembly 1300 can be stowed over the headband 1200 when not in use, as illustrated in Fig. lc.

Changing the angle between the nozzle assembly 1300 and the headband 1200, removing the nozzle assembly 1300, or stowing the nozzle assembly 1300 over the headband 1200 when not in use, as illustrated in Fig. lc affects the acoustic characteristics of the head wearable air purifier 1000. Specifically, changing the position of, or removing, the nozzle assembly 1300 affects the sound of a wearer's voice which may be noticeable when the user is, for example, talking to someone via a telephony system of the head wearable air purifier 1000. For example, the position or presence of the nozzle assembly 1300 can affect the frequency response of a microphone detecting a user's voice, as shown in Fig. 6.

The nozzle assembly 1300 essentially comprises an elongate, hollow tube that is arranged so that it can be fluidically connected between the air outlet 1104a of the first ear cup 1100a and the air outlet 1104b of the second ear cup 1100b, with a first air inlet or ingress port 1301 being provided by a first open end of the nozzle assembly 1300 and a second air inlet or ingress port 1302 being provided by an opposite, second open end of the nozzle assembly 1300. The first air inlet or ingress port 1301 of the nozzle assembly 1300 is therefore arranged to be able to receive the filtered airflow emitted from the air outlet 1104a of the first ear cup 1100a and the second air inlet or ingress port 1302 of the nozzle assembly 1300 is arranged to be able to the receive the filtered airflow emitted from the air outlet 1104b of the second ear cup 1100b. The nozzle assembly 1300 is arranged such that, when the purifier 1000 is worn by a user with the first ear cup 1100a over a first ear of the user and the second ear cup 1100b over a second ear of the user and with the nozzle assembly 1300 in the first end position, the nozzle assembly 1300 will extend around a face of the user, from one side to the other, and in front of a mouth of the user. In particular, the nozzle assembly 1300 extends around the jaw of the user, from adjacent to one cheek to adjacent the other cheek, without making contact with the mouth, nose or surrounding regions of the user's face.

The nozzle assembly 1300 is provided with an air outlet 1310 for emitting/delivering the filtered air to a user. For example, an array of apertures may provide the air outlet 1310, and may be formed in a section of the nozzle assembly 1300 that is centred at the centre of the second outer surface 1308 of the nozzle assembly 1300 that faces towards the ear cups 1100a, 1100b. The apertures are therefore only present in in a section of the nozzle assembly 1300 that, when the purifier 1000 is worn by a user, faces towards the mouth and nose of the user.

Advantageously, the ear cup 1100 is arranged so that the revolution of the rigid outlet duct 1115 around the periphery of the speaker housing 1102 is independent of the impeller casing 1108, such that it can revolve relative to both the speaker housing 1102 and to the impeller casing 1108. This arrangement provides that the nozzle assembly 1300 can be rotated towards and stowed over the headband 1200 when not in use without the need for any of the components that are internal to the speaker housing 1102 to be rotatable relative to the speaker housing 1102, which would complicate the construction of the ear cup 1100.

The nozzle assembly 1300 may also be placed in other positions, for example including a dipped' position wherein the air outlet is away from the nose and mouth of a user (e.g., around or below a user's chin) but the nozzle assembly 1300 is still usable and connected to the ear cup 1100.

A first external microphone 1142 is provided on the inner surface of the circular front surface 1135c of the filter seat 1135. The first external microphone 1142 is arranged to provide data to the control circuit 1114. The first external microphone is provided towards the exterior of the speaker assembly in order to detect any background or ambient noise. A first external microphone may also be referred to as a reference microphone. Providing the ear cup 1100 with a first external microphone 1142 is particularly useful, as it provides that noise generated by the motor 1110 and/or the impeller 1109 can be detected by the first external microphone 1142 and removed from an audio signal. A voice microphone (which may be referred to herein as a second external microphone) may be arranged in a similar manner to the first external microphone H42, on an inner surface of the ear cup 1100 and acoustically coupled to the exterior of the speaker assembly in order to detect the voice of a wearer. For example, it may be positioned in a suitable location which is near to the mouth of a wearer.

The control circuit 1114 of the ear cups 1100a, 1100b is arranged to control a rotational speed of the motor 1110 such that the maximum rotational speed of the impeller 1109 is from 9000 to 18,000 RPM, is preferably from 10,000 to 14,000 RPM, and is more preferably from 10,000 to 12,000 RPM.

Fig. 3 is a flow chart showing a method 100 of operating a head wearable air purifier, for example the head wearable air purifier 1000 as described above with respect to Figs. 1 and 2. For example, the method may be implemented by the controller 1114. The method 100 is used to account for acoustic characteristics of the head wearable air purifier in an audio signal, specifically acoustic characteristics which are affected by a physical state of the head wearable air purifier. Such acoustic characteristics may include the noise generated by a fan assembly (for example, noise generated by airflow, and/or by rotation of a motor and/or an impeller of the fan assembly), or an impact of the physical state of the head wearable air purifier on a frequency response, for example changing the way a wearer's voice sounds over a telephony system. Although the steps of the method 100 are described in a particular order below, it will be appreciated that steps of the method 100 may be carried out in any suitable order.

The method 100 comprises determining 110 a physical state of the head wearable air purifier amongst a plurality of known physical states, each known physical state producing different acoustic characteristics of the head wearable air purifier. For example, determining 110 a physical state of the head wearable air purifier may comprise determining a rotational speed of a fan assembly (e.g., a rotation speed of a motor, such as motor 1110, or an impeller, such as impeller 1109), or determining a position or presence of a nozzle assembly (for example determining whether the nozzle assembly 1300 is in use as shown in Fig. la or stowed over the headband as shown in Fig. 1c).

The method 100 further comprises receiving 120 an audio signal. The audio signal may be a signal which is affected by the acoustic characteristics of the head wearable air purifier due to the physical state. For example, the audio signal may include unwanted or undesirable noise due to the fan assembly, and/or the audio signal may be distorted (e.g., changes in frequency and/or amplitude) by the acoustic characteristics.

In order to account for the acoustic characteristics of the head wearable air purifier, an audio profile is obtained 130 and the audio signal is modified 140 based on the audio profile. The audio profile is configured such that modifying the audio signal compensates for the acoustic characteristics of the head wearable air purifier, thereby modifying the audio signal in such a way as to reflect the 'true' sound of the source of the audio signal. For example, the audio profile may be configured to remove unwanted or undesirable noise (e.g., resulting from rotation of the fan assembly), or may be configured to compensate for a distortion in the audio signal.

It will be appreciated that modifying 140 the audio signal may, in certain embodiments, further comprise modifications in addition to applying the audio profile. For example, modifying 140 the audio signal may further comprise applying a noise reduction algorithm, such as a wind noise reduction algorithm.

The method 100 further comprises a step of outputting 150 the modified audio signal. For example, this may comprise outputting the modified audio signal to a speaker assembly of the head wearable air purifier (for example, by operating the speaker assembly according to the modified audio signal), or outputting the modified audio signal to a telephony system of the head wearable air purifier.

Fig. 4 is a schematic diagram of a method 200 according to an embodiment of the present invention. For example, the method 200 may be applied to a head wearable air purifier 1000 as described above with respect to Figs. 1 and 2. The method 200 generally comprises receiving an audio signal 210, modifying the audio signal 220, and outputting the modified audio signal 230.

Receiving the audio signal 210 comprises detecting sound at each of three microphones and generating a digital audio signal by a respective digital-analogue converter (DAC).

The three microphones comprise a first external microphone 211a for detecting ambient noise from an environment about the head wearable air purifier, a voice microphone 212a for detecting the voice of a wearer, and a fan assembly noise microphone 213a for detecting noise generated by a fan assembly (e.g., by rotation of a motor and/or an impeller of a fan assembly). Each of the three microphones 211a, 212a, 213a has a corresponding DAC 21 lb, 212h, 213b for producing the audio signal (as a digital signal) from the sound detected by the microphone. The first external microphone 211a and the voice microphone 212a are external microphones, in that they are acoustically connected to an environment outside of the speaker assembly in order to detect ambient noise and a wearer's voice, respectively, and the fan assembly noise microphone 213a is an internal microphone, and is acoustically connected to the environment internal of the speaker assembly.

Modifying 220 the audio signal comprises applying beamforming and noise reduction algorithms, determining a physical state of the head wearable air purifier and obtaining an associated audio profile, and applying an equalisation and/or compression profile.

Specifically, a beamforming algorithm 221 is applied to audio signals received from the FF ANC headphone 211a and DAC 211b, and from the voice microphone 212a and DAC 212b. For example, the beamforming algorithm 221 may be used to focus the audio signal to a voice, such as the voice of a wearer, and diminish the presence of other sounds or noise in the audio signal.

One or more noise reduction algorithms 222 may be applied to the audio signal received from the beamforming algorithm 221, as well as to the audio signal received from the fan assembly noise microphone 213a and DAC 213b. For example, the noise reduction algorithm 222 may include a wind noise reduction algorithm. For example, the noise reduction algorithm 222 may be a stationary noise reduction algorithm or a wind noise reduction algorithm which use spectral subtraction techniques. In this embodiment, the noise reduction algorithm 222 is applied to the audio signal in the frequency domain.

In order to determine a physical state of the head wearable air purifier and obtain an associated audio profile, a look-up table is consulted 224. The look-up table associates a compressor speed (i.e., an impeller rotation speed) with coefficients of a biquadratic digital filter ("filter biquads") which can be applied to the audio signal in order to filter out any one or more of a plurality of fundamental or harmonic tones in the audio signal resulting from rotation of the fan assembly. For example, the rotation speed may be determined from software instructions for a controller (e.g., a motor controller) of the fan assembly, or may be determined based on detecting the noise which is generated by the fan assembly (e.g., by analyzing noise detected by the fan assembly noise microphone 213a). As shown in Fig. 4, determining the rotation speed of the fan assembly (in particular, the impeller or compressor) comprises determining whether the impeller is rotation at a low speed, a medium speed, or a high speed, and filter biquads are provided for each predetermined rotation speed to remove associated noise. For example, the filter biquads may define a notch filter as described below with respect to Fig. 7.

Modifying 220 the audio signal then comprises applying the audio profile to the audio signal 223, specifically applying the filter retrieved from the look-up table, in order to remove noise associated with rotation of the fan assembly from the audio signal.

Finally, modifying 220 the audio signal comprises applying an equalisation and/or compression profile 225, which may adjust the audio signal for any other acoustic characteristics of the head wearable air purifier, such as the presence and/or position of a nozzle assembly, to ensure that the outputted audio signal sounds natural.

After modifying 220 the audio signal, the modified audio signal is output 230. In this embodiment, outputting the audio signal 230 comprises outputting the modified audio signal to a telephony system of the head wearable air purifier.

In this way, the method 200 can output a voice of a wearer to a telephony system, wherein 30 the audio signal representing the voice of a wearer as detected by a voice microphone 212a also includes extraneous noise arising from rotation of the fan assembly. However, this extraneous noise is compensated for by determining the rotation speed of the fan assembly and retrieving an associated filter by consulting 224 a look-up table. As the rotation speed of the fan assembly is a predetermined speed (i.e., either low, medium or high), the associated filter is particularly effective at removing the unwanted noise from the audio signal, and removal of said noise is performed with greater computational efficiency. The voice of the wearer as detected by the voice microphone 212a may also be affected by acoustic characteristics of a nozzle assembly, which may effect the relative amplitude and frequency of the wearer's voice (e.g., as described below with respect to Fig. 6). The method 200 may correct for such distortions by applying an equalisation and/or compression profile 225, which can ensure that the wearer's voice sounds natural when passed over a telephony system.

Fig. 5 is a schematic diagram of a method 300 according to a further embodiment of the present invention. In particular, the method 300 allows a wearer to hear ambient environmental noises (e.g., such as a person speaking) more clearly when wearing the head wearable air purifier. For example, the method 300 may be applied to a head wearable air purifier 1000 as described above with respect to Figs. 1 and 2. The method 300 generally comprises receiving an audio signal 310, modifying the audio signal 320, and outputting the modified audio signal 330.

Receiving the audio signal 310 comprises detecting sound at each of two microphones and generating a digital audio signal by a respective digital-analogue converter (DAC). The two microphones comprise a first external microphone 311a for detecting ambient noise from an environment about the head wearable air purifier, and a fan assembly noise microphone 312a for detecting noise generated by a fan assembly (e.g., by rotation of a motor and/or an impeller of a fan assembly). Each of the microphones 311a, 312a has a corresponding DAC 311b, 312b for producing the audio signal (as a digital signal) from the sound detected by the microphone. For example, the first external microphone 311a may detect speech of a person talking to a wearer of the head wearable air purifier. The first external microphone 311a is an external microphone, in that it is acoustically connected to an environment outside of the speaker assembly in order to detect ambient noise, and the fan assembly noise microphone 312a is an internal microphone, and is acoustically connected to the environment internal of the speaker assembly.

Modifying the audio signal 320 comprises determining a physical state of the head wearable air purifier and obtaining an associated audio profile, applying a noise reduction algorithm, and applying an equalisation and/or compression profile.

Specifically, in order to determine a physical state of the head wearable air purifier and an associated audio profile, a look-up table is consulted 322. The look-up table associates a compressor speed (i.e., an impeller rotation speed) with coefficients of a biquadratic digital filter ("filter biquads") which can be applied to the audio signal in order to filter out any one or more of a plurality of fundamental or harmonic tones in the audio signal resulting from rotation of the fan assembly. For example, the rotation speed may be determined from software instructions for a controller (e.g., a motor controller) of the fan assembly, or may be determined based on detecting the noise which is generated by the fan assembly (e.g., by analyzing noise detected by the fan assembly noise microphone 312a). As shown in Fig. 5, determining the rotation speed of the fan assembly (in particular, the impeller or compressor) comprises determining whether the impeller is rotation at a low speed, a medium speed, or a high speed, and filter biquads are provided for each predetermined rotation speed to remove associated noise. For example, the filter biquads may define a notch filter as described below with respect to Fig. 7.

Modifying 320 the audio signal then comprises applying the audio profile to the audio signal 321, specifically applying the filter retrieved from the look-up table, in order to remove noise associated with rotation of the fan assembly from the audio signal.

For example, the first external microphone 311a may detect the voice of a person speaking to the wearer of the head wearable air purifier, though the sound detected by the first external microphone 311a (and heard by the wearer) may be overlaid with noise generated by the fan assembly. By applying the associated audio profile (i.e., a filter as determined by the look-up table), this noise may be removed from the speech.

One or more noise reduction algorithms 323 are then applied to the audio signal. For example, the noise reduction algorithm may include a noise reduction algorithm. In this embodiment, the noise reduction algorithm is applied to the audio signal in the time domain, as reduced latency is important to ensure that there is little audio delay detectable by the wearer hearing the audio signal as it is output by the speaker assembly of the head wearable air purifier.

Modifying the audio signal 320 further comprises applying an equalisation and/or compression profile 324, which may adjust the audio signal for any other acoustic characteristics of the head wearable air purifier, such as the presence and/or position of a nozzle assembly, to ensure that the outputted modified audio signal sounds natural.

After modifying the audio signal 320, the modified audio signal is output 330. In this example, outputting the audio signal 330 comprises operating a speaker assembly of the head wearable air purifier according to the modified audio signal. In this way, the user may hear ambient sounds while still wearing the head wearable air purifier. In particular, the method 300 allows a wearer to hear the ambient sounds without distortions which are introduced by the physical state of the head wearable air purifier. For example, noise produced by rotation of the fan assembly is removed from the audio signal which is heard by the wearer. Such ambient sound may include speech of another person, for example.

Fig. 6 is a graph 400 which shows how the presence of a nozzle assembly can affect the voice of a wearer of a head wearable air purifier (e.g., the head wearable air purifier 1000 shown in Figs. 1 and 2). The graph 400 shows the amplitude of sound detected by a voice microphone against the frequency of sound across a wideband frequency range of 50 Hz to 7 kHz.

A first line 410 shows the frequency response for a head wearable air purifier with no nozzle assembly present, and a second line 420 shows the frequency response with a nozzle assembly present. It will be appreciated that similar frequency response curves may also be obtained for different positions of the nozzle assembly (e.g., a curve may also be obtained with a nozzle assembly in a stowed position). As shown in Fig. 6, the physical state of the head wearable air purifier, in this example the presence or absence of a nozzle assembly, affects the acoustic characteristics of the head wearable air purifier, in this example by changing the detected frequencies in a wearer's voice. The audio signal (e.g., audio signal from a voice microphone) can be modified compensate for these distortions, in particular, by applying an audio profile comprising a suitable equalisation profile. It will also be appreciated that the physical state of the head wearable air purifier may also be determined by observing the detected frequencies. For example, if the detected frequency response is similar to the first line 410 then it may be determined that the nozzle assembly is not present, and if the detected frequency response is similar to the second line 420 then it may be determined that the nozzle assembly is present.

Fig. 7 is a graph 500 showing a notch filter which may be used as an audio profile in embodiments of the present invention. In particular, the notch filter may be used to filter out a fundamental or harmonic tone resulting from rotation of a fan assembly (e.g., an impeller or a motor of a fan assembly) from an audio signal. For example, such a notch filter may be used in methods described above with respect to Figs. 4 and 5.

The notch filter is configured to reduce the amplitude of sound between a low cut-off frequency Fl and a high cut-off frequency F2, wherein the range Fl to F2 is centred on a middle frequency Hl. The bandwidth of the notch filter may be determined according to a frequency of the fundamental or harmonic tone and the precision to which a rotation speed of the fan assembly is determined. In particular, the precision to which a rotation speed of the fan assembly is determined may be dependent upon the precision to which a rotation speed of the fan assembly is controlled, for example where the rotation speed is determined from software instructions for a controller (e.g., a motor controller) of the fan assembly. For example, if the rotation speed of the fan can be determined (e.g., controlled) to +/-5% of a desired value, and the frequency of noise generated is 100 Hz, then the bandwidth of the notch filter may he 10 Hz (i.e., F2-F1 = 10Hz) , and if the frequency of the noise generated is 500 Hz then the bandwidth of the notch filter may be 50 Hz (i.e., F2-F1 = 50 Hz). Filter biquadratics which define a notch filter for a predetermined physical state of the head wearable air purifier may be stored in a look-up table, for example as described above with respect to Figs. 4 and 5.

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof While the invention has been described in conjunction with the exemplary embodiments have been described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention as defined by the claims.

Claims

CLAIMS1. A method of operating a head wearable air purifier comprising a speaker assembly, a microphone assembly and a fan assembly operable to generate filtered airflow and discharge the filtered airflow towards the face of a wearer, wherein the method comprises: determining a physical state of the head wearable air purifier amongst a plurality of known physical states, each known physical state producing different acoustic characteristics of the head wearable air purifier; receiving an audio signal from the microphone assembly; obtaining an audio profile associated with the determined physical state of the head wearable air purifier; modifying the audio signal based on the audio profile; and outputting the modified audio signal.
2. The method of claim 1, wherein the determining the physical state of the head wearable air purifier comprises determining a rotational speed of the fan assembly.
3. The method of claim 2, wherein the determining the rotation speed of the fan assembly comprises determining a predetermined rotation speed of the fan assembly based on a known rotation speed setting of the fan assembly.
4. The method of claim 3, wherein the determining the rotation speed of the fan assembly comprises determining whether the fan assembly is not rotating, rotating at a low speed, rotating at a medium speed, or rotating at a high speed.
5. The method of any one of claims 2 to claim 4, wherein the audio profile comprises a filter to be applied to the audio signal to remove unwanted noise introduced to the audio signal by rotation of the fan assembly.
6. The method of claim 5, wherein the filter is a notch filter configured to filter out any one or more of a plurality of fundamental or harmonic tones in the audio signal resulting from rotation of the fan assembly.
7. The method of claim 6, wherein a bandwidth of the notch filter is determined according to a frequency of the fundamental or harmonic tone and the precision to which a rotation speed of the fan assembly is determined.
8. The method of any one of claims 2 to 7, wherein the modifying the audio signal further comprises applying a noise reduction algorithm.
9. The method of any preceding claim, wherein the determining the physical state of the head wearable air purifier comprises determining a presence of and/or a position of a nozzle assembly, wherein the nozzle assembly is attachable to the fan assembly to receive airflow generated by the fan assembly and discharge the airflow towards a face of a wearer.
10. The method of claim 9, wherein the audio profile comprises an equalisation profile to be applied to the audio signal to compensate for distortions in the sound represented by the audio signal by the nozzle assembly.
1 1. The method of claim 10, wherein the equalisation profile is configured to adjust the gain and/or the frequency response.
12. The method of any preceding claim wherein the audio signal is received from at least one of an external microphone of the head wearable air purifier configured to target detection of a wearer's voice or an external microphone of the head wearable air purifier configured to target detection of sound from an environment surrounding the head wearable air purifier.
13. The method of any preceding claim, wherein the outputting the modified audio signal comprises outputting the modified audio signal to the speaker assembly.
14. The method of clam 13, wherein the modifying the audio signal further comprises applying a noise reductive algorithm, and wherein the noise reduction algorithm is applied in the time domain.
15. The method of claim 13 or clam 14, wherein the modifying the audio signal further comprises applying an equalisation profile and/or a compression profile.
16. The method of any preceding claim, wherein the outputting the modified audio signal comprises outputting the modified audio signal to a telephony system of the head wearable air purifier.
17. The method of claim 15, wherein the modifying the audio signal further comprises applying a noise reduction algorithm, and wherein the noise reduction algorithm is applied in the frequency domain.
18. The method of claim 15 or claim 16, wherein the modifying the audio signal further comprises applying a beamforming algorithm.
19. A head wearable air purifier comprising: a speaker assembly arranged to be worn by a wearer, a fan assembly operable to generate filtered airflow and discharge the filtered airflow towards the face of a wearer; a microphone assembly for obtaining an audio signal; and a controller configured to perform a method according to any one of the preceding claims.
20. The head wearable air purifier of claim 19, further comprising a nozzle assembly, the nozzle assembly comprising an air inlet for receiving a purified airflow from the fan assembly and an air outlet for directing the purified airflow towards a wearer's mouth, wherein the nozzle assembly is removably attachable to the head wearable air purifier.
21. The head wearable air purifier of claim 19 or claim 20, wherein the microphone assembly comprises at least one of: a microphone which is internal to the speaker assembly; and/or a microphone which is external to the speaker assembly.
22. The head wearable air purifier of claim 21, wherein the microphone assembly comprises a first external microphone for detecting ambient sound and noise, a second external microphone for detecting the voice of a wearer, and an internal microphone for detecting noise from the fan assembly.